1721: Strange Country

There is a country with N cities, some of which are connected with bidirectional roads. Your task is to reconfigure the roads so that it is possible to get from each city to every other city. You must do this using the minimum possible number of transformations, where each transformation consists of the following steps: Choose four different cities A, B, C and D, where roads (A, B) and (C, D) exist, but (A, C), (A, D), (B, C) and (B, D) do not exist. Destroy roads (A, B) and (C, D). Build two new roads - either (A, C) and (B, D), or (A, D) and (B, C). The following images show an example of this transformation. From the first situation you can get the second one or the third one: You are given a map[i][j], map[i][j] is ‘Y‘ if there is a road between cities i and j, and ‘N‘ otherwise. Return minimal number of transformations required to accomplish your task, or return -1 if it is impossible. Constraints - 2<=N<=50 - For each i and j, map[i][j] will be equal to map[j][i]. - For each i, map[i][i] will be equal to ‘N‘.

*Line 1: N *Line 2...1+N: The jth element of line i describing map[i][j]

*Line 1: A single integer that the minimal number of transformations required

2
NY
YN
5
NYYNN
YNYNN
YYNNN
NNNNY
NNNYN

0
1

The second sample transformations is like the images followed